THIELAVIOPSIS PARADOXA, 565 



given when estimating the effect of a fungicide upon fungus 

 spores. Brooks (19) states that his charts of results are based 

 entirely upon the data secured on the first and second days 

 lifter transferring, and that in very few instances did spores 

 germinate on the second day. In the present instance any 

 arbitrary limitation of the period of observation to two or 

 three days would certainly have resulted in an entirely 

 erroneous estimate of the fungicidal value of formalin. To 

 arrive at the true value the cultures must be left until no 

 further germination occui's. This retardation of germination 

 is more marked with formalin than with any of the other 

 substances tested in this series of experiments. A • 1 per cent, 

 solution of formaldehyde is now being largely recommended 

 as a disinfectant for seeds, but in view of the foregoing results 

 it would seem that its retarding effect has been mistaken for 

 actual kilHng. In a recent study of the fungi occurring on 

 wheat stems, it is stated that the stems " were steriUzed by 

 treating one minute with 1 per cent, formaldeliyde, and 

 afterwards washing with sterile distilled water. Thus it is 

 presumed that all saprophytes and surface fungi were 

 eradicated." As the fungi in question included species of 

 Macrosporium and Helrninthosporium, it is highly probable 

 that this method is fallacious. 



Carbolic Acid, 1 per Cent. 



(1) As a preliminary experiment, the spores were immersed 

 in the solution in the manner already described, and transferred 

 by a platinum loop every five minutes for one hour, and at the 

 end of every hour for the succeeding twelve hours. The spores 

 transferred after five minutes' immersion developed a good 

 growth in two days, while those transferred after ten minutes' 

 immersion developed a good growth in three days. No growth 

 occurred in any of the remaining flasks. The spores were there- 

 fore killed by an immersion of between ten and fifteen minutes. 



(2) An attempt was next made to determine whether the 

 age of the culture affected the time required to kill the spores. 

 Three cultures were employed : the first eight days old, the 

 second twenty days, and the third thirty-three days. The 

 spores were transferred as above by a platinum loop. In the 



6(11)10 (73) 



